https://www.crazyguyonabike.com/doc/...oc_id=6090&v=w

shows another option I have used for many years in the past when my forks did not have mounting eyelets. There are some photos down the page showing how you can use a U bolt to mount to the fork to support the weight, and some brackets which attach to the brake attachment points to stop the rack rotating. The brackets are easy to make or to get someone to make them for you.